The present invention relates to an electromagnetically controlled valve for a two-cycle engine, such valve being adapted to be received within a scavenge port of a cylinder for controlling the operation of the engine and more particularly, a valve which permits the purging of a determinable amount of fluid from the cylinder such that a proper air/fuel ratio is maintained.
Advantages of a two cycle engine are reduced cost and simplicity of construction. These engines, however, do have significant drawbacks. There is always some residual, sometimes significant, amount of burnt gases that remain in the cylinder and mix with a fresh charge of air and fuel. Consequently, the power generated by the two-cycle engine is less than it could be if all of the burnt gases where exhausted. In addition, because of the intake and exhaust port arrangement in a conventional engine, the exhaust gases contain large amounts of hydrocarbons and with regard to a two-cycle carburetted engine, raw gas enters directly into the exhaust system.
Further, the performance of a two-cycle engine, especially at low demand conditions such as idle, cruise or coast conditions, is less than desirable and is characterized by excessive stumble and miss firing. This shortcoming can be seen from the following. During idle conditions, that is, when the throttle is virtually closed only a relative small amount of clean air is permitted to enter the combustion chamber. Subsequently, during ignition, the ratio of air to the exhaust gas within the combustion chamber is not sufficient to encourage combustion. During low demand conditions it is not uncommon for a two-cycle engine to misfire four out of five times.
It is an object of the present invention to improve the performance of a two-cycle engine. A further object of the present invention is to selectively control the amount of exhaust gases residing within the combustion chamber of the two-cycle engine such that proper ignition takes place. A further object of the invention is to selectively purge a predetermined amount of working fluid from the cylinder to regulate the effective air/fuel ratio. A further object is to provide a scavenge valve for regulating the performance of a two-cycle engine.
Accordingly the present invention comprises: a valve for use in controlling the amount of working fluid purged from a cylinder of an engine prior to combustion, comprising: a piston received in and forming part of a chamber in a housing; the housing including an aperture formed about the chamber and an inlet upstream of the aperture, such piston being movable between first and second positions to open and close communication between the aperture and an inlet, the inlet adapted to receive pressurized fluid. The valve further including first means for selectively establishing and terminating communication of the chamber with an outlet adapted to be communicated with pressure lower than a pressure applied to an upstream side of the piston, whereby when communication is established a pressure force differential is created across the piston to urge same downstream, toward the first position, to uncover the apertures to permit flow from the inlet through the aperture; means for balancing the pressure forces acting on upstream and downstream surfaces of the piston, such balancing means effective during intervals when the first means terminates communication of the chamber to the outlet; and means for urging the piston in an upstream direction toward the second position to prohibit flow from the inlet through the aperture.
Many other objects and purposes of the invention will be clear from the following detailed description of the drawings.